1. Field of the Invention
The present invention generally relates to a method for forming a semiconductor structure, and more particularly, to a method for forming a semiconductor structure using planarization process.
2. Description of the Prior Art
Integrated circuits (ICs) are typically formed on substrates, exemplarily silicon wafers, by sequential deposition of conductive, semi-conductive or insulating layers. After depositing the required layer, etching process is often performed to create circuitry features and followed by another film/layer formation. Consequently, the topmost surface of the substrate may become non-planar across its surface and requires planarization.
Chemical-mechanical polishing (hereinafter abbreviated as CMP) is one accepted method of planarization and now typically employed in the industry. In general, CMP involves pressing a surface of the substrate against a polishing pad that is mounted upon a circular turning platen with a polishing head tightly holds the substrate. Slurries, usually either are basic or acidic and generally contain particles, are delivered to the center of the polishing pad to chemically passivate or oxidize the surface being polished and abrasively remove or polish off the surface of the substrate. The interaction of the polishing pad and the slurries with the surface being polished results in controlled polishing of the desired surface for subsequent processes.
Typically, CMP process maybe carried out on separated platens, even in separate CMP systems because different slurry compositions/chemistries are needed to polish different layers. Furthermore, to obtain a precise stop surface, different stop layers are required. That is, CMP requires multiple and complicated steps. In other words, steps of CMP process are complicated. As compared to a hypothetical single step process, such multi-stepped process adds to cycle time, adds to fabrication cost, and can increase defect density. Therefore CMP processes or pre-CMP processes with reduced step number are in need.